I used Stanadyne performance formula in my 05 and it made a significant difference, esp. in smoothness and runability. In fact I used to swear by it. Since I have about 1/2 a gallon left over from that truck I have tried it in my LML, it does not seem to have the same pronounced effect. In fact I think the LML runs posssibly better without it. Owners manual does not condone additives and it downright forbids any that contain alcohol. That said, I might still use it when it gets real cold and mabie once in a while to help condition or help clean out the system, but I don't think it is a necessity like it was with my 05. Plus, it was costing me the equivalent of 15 cents a gallon more to use it!